Jeff Prowant has become accustomed to referring to various oak-covered ridges in central Pennsylvania by the names of the companies that hold natural gas leases here. Prowant, district manager for Tiadaghton State Forest, oversees 155,000 acres of wooded plateaus and the valleys and brook-trout streams in between. Sweeping his arm across the vista, he says, “The near ridge is PGE [Pennsylvania General Energy]. The rest of it’s Anadarko.”

A forester by training, Prowant supervises selective commercial timbering and manages the trails and wildlife that attract some 200,000 hikers, hunters, and anglers each year. Since 2008 he’s been tasked with balancing these traditional uses with horizontal drilling and hydraulic fracturing for natural gas in the Marcellus Shale, a layer of porous black rock a mile and a half beneath where we stand.

“They call this the sweet spot,” Prowant says. The 95,000-square-mile Marcellus underlies two-thirds of Pennsylvania, plus portions of New York, Ohio, and West Virginia. It’s the richest gas field in the country, but not all drill sites are equal. Tiadaghton is a gateway to especially abundant deposits close to a major pipeline.

It’s also a shady nursery for trillium, salamanders, and such songbirds as scarlet tanagers and black-throated blue warblers. Audubon Pennsylvania scientists have identified a 4 million-acre region near the headwaters of the Susquehanna River, including Tiadaghton, as the largest intact remnant of woodland in the state—a place once called Penn’s Woods and described by an early settler as “nothing but an undulating surface of impenetrable forest.” Pennsylvania Governor Tom Corbett has signaled that he may lift a 2010 moratorium on new state-land leases, which would open the yet-undeveloped heart of the Susquehanna headwaters, an area Audubon deems critical bird habitat, to energy development.

Tiadaghton is just one of Pennsylvania’s forests now fragmented by wells, pipelines, and tanker-truck roads, with more on the way. A quarter of the 7,000 horizontal wells drilled in the state since 2007, when the boom began, disrupt core forest, according to a Penn State analysis. Companies plan to build an additional 15,000 well pads for fracking by 2030, which would require 25,000 more miles of gathering lines, half of them through woods. Penn State estimates that well pads cover 3,400 forested acres in the state; the Nature Conservancy calculates that when you include new roads and gas and water lines, 18,500 total forested acres have been disturbed. Gathering lines connect remote wells to main pipes and, eventually, to the Northeast’s energy markets. Collectively they disturb more land than all other drilling infrastructure. Linear clearcuts usher these pipelines over hills and under rivers.

Each gas well pad in Tiadaghton flattens four to eight football fields of trees and is lighted 24/7 during drilling and fracking. “It’s like dropping Walmart parking lots in the woods,” says Margaret Brittingham, a wildlife resources professor at Penn State. She and graduate students are surveying birds, salamanders, and frogs around pads. So far they’ve seen an increase in common backyard species like robins, and a decline in warblers and other animals adapted to unbroken tree cover.

In Tiadaghton’s rugged terrain, fresh pipeline clearings can be as stark and wide as ski slopes. Amber Oyler, an environmental manager for PGE, stands at the edge of a 125-foot-wide cut on the side of Tiadaghton’s Huntley Mountain. “It had to be this wide because of the topography and the method they had to use to get all the equipment up,” she explains. The pipe lies four to 20 feet below ground. To keep roots from penetrating, PGE mows a 40-foot-wide swath every three to five years.

Nathan Bennett, a geologist with neighboring lessee Anadarko Petroleum Corporation, says companies rarely reduce their footprint by sharing this kind of infrastructure. “There’s not a whole lot of extra room to take somebody else’s gas into our pipeline.”

The effects of well-pad and pipeline clearing reach as far as 300 feet into neighboring forest, making it drier, warmer, brighter—more available to invasive species and nest predators such as crows, cowbirds, and raccoons.

Rigs, trucks, and job-site trailers occupy well pads for months during initial drilling. But once the gas starts flowing, the sites quiet and darken. That’s when forest manager Prowant urges companies to remove some of the gravel so that the ground can be more valuable to wildlife. But state rules give him little leverage, and so far no companies in Tiadaghton have done so. Prowant estimates it could take decades to restore mature grassland, a century to restore forest.

Editorial note: A fracking moratorium in neighboring New York remains in place as Governor Andrew Cuomo decides whether to allow it at all. The governor announced in mid-December that a final decision won’t be made until after the 2014 elections. If the state does allow drilling, says Audubon New York’s government relations director Sean Mahar, it should declare Important Bird Areas and public lands off-limits to all aspects of natural gas development—including pipelines.

Speak Up!

Tell Pennsylvania Governor Tom Corbett and New York Governor Andrew Cuomo that natural gas development should not come at the cost of breaking up some of the most valuable songbird nurseries on the Atlantic Flyway. For the latest on this issue, go to New York Audubon.